Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
2000-05-31
2002-04-02
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S403000, C523S400000, C252S405000, C252S406000, C252S407000
Reexamination Certificate
active
06365707
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a resin used for optical materials such as plastic lenses, prisms, optical fibers, information recording substrates, filters and light emitting diodes and also to a polymerizable composition which serves as a raw material of the resin. In particular, the invention relates to a polymerizable composition suited as a raw material for eyeglass plastic lenses.
2. Description of the Related Art
Plastic lenses are lightweight and non-brittle compared with inorganic glass lenses, and dyeable, and are therefore rapidly prevailing in the areas of optical devices such as eyeglass lenses and camera lenses in recent years. The plastic lenses have been required to have a high refractive index and a high Abbe number as optical performances and to have high heat resistance, a low specific gravity and processability as physical properties.
Among these performances, the requirement for a high heat resistance and low specific gravity have been satisfied on a high level in high-refractive-index plastic lenses produced at present. Resins widely employed these days for such purposes include a radical polymerization product of diethylene glycol bis(allylcarbonate) (which will hereinafter be abbreviated as “D.A.C.”). This resin has various advantages such as excellent impact resistance, lightweight, superb tintability, and good processability such as good cutting and grinding machinability. Its refractive index, however, is about 1.50 nd so that the peripheral thickness inevitably becomes large. There is accordingly a desire for the development of a lens resin having a still higher refractive index.
As a resin imparted with a higher refractive index than the D.A.C. resin, known is a polythiourethane resin (Japanese Patent Publication No. 58489/1992) having a sulfur atom introduced into the resin, a sulfur-containing O-(meth)acrylate resin (Japanese Patent Laid-Open No. 16140/1992) or a thio(meth)acrylate resin (Japanese Patent Publication No. 59060/1991). The polythiourethane resin is well balanced with a high refractive index and good impact resistance.
It is however very difficult to improve both refractive index and Abbe number simultaneously, because these physical properties are contrary to each other and the Abbe number decreases with a rise in the refractive index. Heightening of the refractive index while suppressing a reduction in the Abbe number is therefore studied briskly.
Among various studies, one of the most typical proposals is for a high-refractive-index lens resin using an episulfide compound, for example, in Japanese Patent Laid-Open Nos. 110979/1997, 71580/1997, 255781/1997, 2982878/1998, 166037/1999, WO89/10575, 140070/1999, 183702/1999, and 189592/1999 or Japanese Patent Application No. 68448/1999.
The process as described in such a literature makes it possible to provide a resin having a high refractive index while maintaining a relatively high Abbe number. When a resin is prepared by any one of the above-described processes, however, the pot life of the monomer is not sufficient upon polymerization, which prevents smooth polymerization work; or considerable heat released upon polymerization happens to cause yellowing or burning of the resin or polymerization runaway. A post-heating step such as annealing also happens to cause yellowing of the resin. In the industrial production of lenses, a yield of 90% or greater is generally required. In the small-quantity production of lenses using an episulfide compound, it is relatively easy to suppress heat release upon polymerization. Upon mass production of lenses, on the other hand, it is difficult to completely control the polymerization for all the lenses and thermal unevenness appears in some of the lenses during polymerization, leading to formation of optical inhomogeneity (which will hereinafter be called “striae”) in these lens thus obtained. Owing to striae, a yield of the lenses sometimes lowers.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a polymerizable composition imparted with a sufficiently long pot life and capable of controlling the heat release upon polymerization; and a resin available therefrom, which is reduced in yellowing upon heating and improved in the hue while having a high refractive index and a high Abbe number, and has effects, when used for the production of lenses, for suppressing the formation of striae inside of the lenses, thereby preventing a yield lowering which otherwise occurs due to striae.
With the foregoing in view, the present inventors have carried out an extensive investigation in order to attain the above-described object. As a result, it has been found that the polymerizable composition according to the present invention is equipped with sufficiently long pot life; and the resin available therefrom is, while having a high refractive index and well-balanced Abbe number, reduced in yellowing upon heating and improved in the hue owing to suppression of heat release upon polymerization, and has effects, in the mass- production of lenses, for suppressing the formation of striae inside of the lenses, thereby preventing a yield lowering, which otherwise occurs due to striae, leading to completion of the present invention.
The present invention therefore provides:
(A) a polymerizable composition comprising a compound (a) having at least one structure represented by the following formula (1):
wherein R
1
is a divalent hydrocarbon group having 1 to 10 carbon atoms, R
2
, R
3
and R
4
each independently represents a hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom; X stands for an S or O atom and the average number of S atom is at least 50% based on the total number of S and O atoms which consist of the three membered ring; and X′ is —S— or —O—,
at least two compounds (b) having a tertiary amino group substituted with aliphatic and/or aromatic group(s) which are each different in catalytic activity as a polymerization catalyst,
with the proviso that the ratio of the total of the tertiary amino groups in the at least two compounds (b) to the episulfide groups in the compound (a) is in the range of 0.0001 to 0.02 in terms of a molar ratio of amino/episulfide functional group,
(B) the polymerizable composition of (A), wherein the compound (a) has at least one structure represented by the following formula (2):
wherein, R
5
represents a divalent hydrocarbon group having 1 to 10 carbon atoms, R
6
, R
7
and R
8
each independently represents a hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom, and X stands for an S or O atom, the average number of the S atom being at least 50% based on the total number of S and O atoms which constitute the three-membered ring,
(C) the polymerizable composition of (A), wherein the compound (a) is represented by the following formula (3):
wherein, R
9
to R
14
each independently represents a hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom, Y represents a substituted or unsubstituted, linear or branched divalent hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted 1,4-dithian group or an arylene group, m stands for an integer of 0 to 2, n stands for an integer of 0 to 4, and Xs each stands for an S or O atom,
(D) the polymerizable composition of (A), wherein the compound (a) is represented by the following formula
wherein, R
15
to R
20
each independently represents a hydrocarbon group having 1 to 10 carbon atom or a hydrogen atom, and Xs each stands for an S or O atom,
(E) the polymerizable composition of (A), wherein the at least two compounds (b) used as a polymerization catalyst and different each other in catalytic activity are at least two compounds selected, respectively, from compounds having high catalytic activity consisting of N,N-dimethylcyclohexylamine and N,N-diethylethanolamine and those having low catalytic activity consisting of N,N-diisopropylethylamine and N-methyldicyclohexylamine,
(F) a resin obtained by heat curing the polymerizable composition of (
Kanemura Yoshinobu
Kawato Nobuo
Kobayashi Seiichi
Morijiri Hiroyuki
Okazaki Koju
Burns Doane , Swecker, Mathis LLP
Mitsui Chemicals Inc.
Truong Duc
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